Bow thruster and windlass

[tensim]

G'day all. We've recently installed a new bow thruster and are looking at options to power it. It's a 24V 250kg thrust unit. We currently have a 24V Muir anchor winch up forward that's fed from our start batteries in the engine room (twin engine vessel), we only drop/raise anchor with the motors running and I've checked at the winch and they get a solid 24V at the terminals.

I'm wondering if I can just "tap" into this existing cable to run power to the thruster? They'll never be used in conjunction so I'm thinking it might be OK? Another option was to install another 24V bank up front, connect the incoming cable from the house batteries to them (I guess creating a larger bank, just separated by a few metres?) then connect the thruster and winch to this new bank?

Or, should I just install a dedicated 24V battery for the thruster? I don't really want to run another set of cables to charge it, so would probably use a 240V charger to top them up (there's an outlet in the locker so that'd be easy)

Thanks for any and all advice, appreciated ? ?

 

[syjos]

Both the windlass and thruster on Sandpiper are powered by a single pair of heavy cables from the start battery bank. Each device has it's own circuit breaker.

I always run the engine while using either device.

Has been wired that way for 22 years without issue.

 

[O C Diver]

Check the amperage of both devices. My bow thruster draws about 4 times the power of the anchor windlass. What you need to calculate is the voltage drop from the batteries to the bow thruster if you used the existing cables. Bow thrusters don't like voltage drop, heat up, and time out much more quickly. Performance of the bow thruster will be much better with 2 modest size batteries in series within a couple of feet of the bow thruster. That's what I did on my boat and the thruster works much better.

Ted

 

[Jeff F]

Agree with Ted. I'd suggest a dedicated battery in the bow supplying both the thruster and windlass, with a dc-dc charger that's powered by the existing wires going to the windlass.



Sent from my moto g play (2021) using Trawler Forum mobile app

 

[dhays]

Agree with Ted. I'd suggest a dedicated battery in the bow supplying both the thruster and windlass, with a dc-dc charger that's powered by the existing wires going to the windlass.

I agree as well. If you have the room in the bow, this would make the most sense. I have a 12v system and power my windlass and bow thruster from a stern battery bank. Not ideal and when that bank needs to be replaced, I’ll likely try just what Jeff suggests.

 

[syjos]

Sandpipers 1980's vintage bow thruster and windlass was originally powered by 2 group 31 batteries in the bow charged by the alternator. The charging cable was undersized so the alternator was unable to adequately provide boost to the thruster.

When I upgraded the windlass, I had a big surplus roll of 4/0 so ran two cables for both hot and ground for kazillian combined amps and added a second 150 amp alternator on the Lehman. Replaced the 8D starting battery with two G31 starting batteries.

At first, I kept the 2 G31's in the bow in parallel, but after testing with and without the bow batteries, removed the bow batteries after not seeing a worthwhile thruster performance improvement.

There is minimal voltage drop through the four 4/0 so truster performance is noticeably stronger than with only the 2 batteries in the bow.

I did experimented with disconnecting two of the 4/0 cables and thruster performance is slightly weaker but still better than two batteries in the bow alone.

After experimenting with the various cable/battery configurations, my conclusion is that if I did not have a huge roll of 4/0 cable (purchased new from a marines store closing liquidation for pennies on the dollar) I would run a pair of 4/0 cables from the start batteries to the bow to power thruster and windlass.

The thruster is 35 years old technology and not very powerful compared to current offerings. I don't use the thruster enough to justify replacement.

There are only two battery banks on Sandpiper. House battery and start. The start batteries supply power to the Lehman, generator, windlass, thruster, 2 radars and autopilot. The two banks can be linked via switch. For emergency start if all batteries die, the first generator I installed had an emergency hand crank. When that generator was replaced with one without a hand crank, I started carrying a jump station battery gizmo.

I've never used the hand crank nor jump station in 22 years.

 

[Mako]

I have used the bow thruster when raising anchor when my bow would fall off in strong winds. So it will just take a little bit of discipline to not use the thruster at the same time as the windlass, if sharing the power.

 

[syjos]

I have used the bow thruster when raising anchor when my bow would fall off in strong winds. So it will just take a little bit of discipline to not use the thruster at the same time as the windlass, if sharing the power.

My wife uses the Lehman to drive up to the anchor as I retrive the anchor from the bow. She is very good manuerving the single without using the thruster.